net.sf.saxon.expr

## Class CastExpression

- java.lang.Object
- - net.sf.saxon.expr.Expression
  - - net.sf.saxon.expr.UnaryExpression
    - - net.sf.saxon.expr.CastingExpression
      - - net.sf.saxon.expr.CastExpression

- All Implemented Interfaces:
    Serializable, SourceLocator, LocationProvider, SaxonLocator, InstructionInfo, Locator

      public class CastExpression
      extends CastingExpression

  Cast Expression: implements "cast as data-type ( expression )". It also allows an internal cast, which has the same semantics as a user-requested cast, but maps an empty sequence to an empty sequence. This expression class does not handle casting to a union type.
  See Also:
    Serialized Form

- - ### Field Summary

    - ### Fields inherited from class net.sf.saxon.expr.CastingExpression

      `converter, nsResolver`

    - ### Fields inherited from class net.sf.saxon.expr.UnaryExpression

      `operand`

    - ### Fields inherited from class net.sf.saxon.expr.Expression

      `EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, INHERITED_CONTEXT, INSPECTION_CONTEXT, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, NAVIGATION_CONTEXT, NODE_VALUE_CONTEXT, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, W3C_CONSUMING, W3C_FREE_RANGING, W3C_GROUP_CONSUMING, W3C_MOTIONLESS, WATCH_METHOD`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `CastExpression(Expression source, AtomicType target, boolean allowEmpty)` Create a cast expression

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `int` | `computeCardinality()` Get the static cardinality of the expression
    `Expression` | `copy()` Copy an expression.
    `boolean` | `equals(Object other)` Is this expression the same as another expression?
    `AtomicValue` | `evaluateItem(XPathContext context)` Evaluate the expression
    `void` | `explain(ExpressionPresenter out)` Diagnostic print of expression structure.
    `ExpressionCompiler` | `getExpressionCompiler()` Return the compiler of the Cast expression
    `IntegerValue[]` | `getIntegerBounds()` For an expression that returns an integer or a sequence of integers, get a lower and upper bound on the values of the integers that may be returned, from static analysis.
    `ItemType` | `getItemType(TypeHierarchy th)` Get the static type of the expression
    `int` | `hashCode()` get HashCode for comparing two expressions.
    `Expression` | `optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)` Perform optimisation of an expression and its subexpressions.
    `protected Expression` | `preEvaluate()` Perform early (compile-time) evaluation
    `String` | `toString()` Represent the expression as a string.
    `Expression` | `typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)` Type-check the expression

    - ### Methods inherited from class net.sf.saxon.expr.CastingExpression

      `allowsEmpty, computeSpecialProperties, getConverter, getNamespaceResolver, getStreamability, getTargetPrimitiveType, getTargetType, isOperandIsStringLiteral, setAllowEmpty, setNamespaceResolver, setOperandIsStringLiteral, setTargetType, simplify`

    - ### Methods inherited from class net.sf.saxon.expr.UnaryExpression

      `displayOperator, getBaseExpression, iterateSubExpressions, promote, replaceSubExpression`

    - ### Methods inherited from class net.sf.saxon.expr.Expression

      `addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getExpressionName, getHostLanguage, getImplementationMethod, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getStreamingAdjunct, getSystemId, getSystemId, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, iterateEvents, iterateSubExpressionInfo, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, toPattern, toStreamingPattern, typeError`

    - ### Methods inherited from class java.lang.Object

      `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- - ### Constructor Detail

    - #### CastExpression

          public CastExpression(Expression source,
                        AtomicType target,
                        boolean allowEmpty)

      Create a cast expression
      Parameters:
        `source` - expression giving the value to be converted
        `target` - the type to which the value is to be converted
        `allowEmpty` - true if the expression allows an empty sequence as input, producing an empty sequence as output. If false, an empty sequence is a type error.

  - ### Method Detail

    - #### typeCheck

          public Expression typeCheck(ExpressionVisitor visitor,
                             ExpressionVisitor.ContextItemType contextItemType)
                               throws XPathException

      Type-check the expression
      Overrides:
        `typeCheck` in class `UnaryExpression`
      Parameters:
        `visitor` - an expression visitor
        `contextItemType` - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to `Type.ITEM_TYPE`
      Returns:
        the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
      Throws:
        `XPathException` - if an error is discovered during this phase (typically a type error)

    - #### optimize

          public Expression optimize(ExpressionVisitor visitor,
                            ExpressionVisitor.ContextItemType contextItemType)
                              throws XPathException

      Perform optimisation of an expression and its subexpressions.

      This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

      Overrides:
        `optimize` in class `UnaryExpression`
      Parameters:
        `visitor` - an expression visitor
        `contextItemType` - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to `Type.ITEM_TYPE`
      Returns:
        the original expression, rewritten if appropriate to optimize execution
      Throws:
        `XPathException` - if an error is discovered during this phase (typically a type error)

    - #### preEvaluate

          protected Expression preEvaluate()
                                    throws XPathException

      Perform early (compile-time) evaluation
      Throws:
        `XPathException`

    - #### computeCardinality

          public int computeCardinality()

      Get the static cardinality of the expression
      Overrides:
        `computeCardinality` in class `UnaryExpression`
      Returns:
        the computed cardinality, as one of the values `StaticProperty.ALLOWS_ZERO_OR_ONE`, `StaticProperty.EXACTLY_ONE`, `StaticProperty.ALLOWS_ONE_OR_MORE`, `StaticProperty.ALLOWS_ZERO_OR_MORE`

    - #### getItemType

          public ItemType getItemType(TypeHierarchy th)

      Get the static type of the expression
      Overrides:
        `getItemType` in class `UnaryExpression`
      Parameters:
        `th` - the type hierarchy cache
      Returns:
        the item type of the items in the result sequence, insofar as this is known statically.

    - #### getIntegerBounds

          public IntegerValue[] getIntegerBounds()

      For an expression that returns an integer or a sequence of integers, get a lower and upper bound on the values of the integers that may be returned, from static analysis. The default implementation returns null, meaning "unknown" or "not applicable". Other implementations return an array of two IntegerValue objects, representing the lower and upper bounds respectively. The values UNBOUNDED_LOWER and UNBOUNDED_UPPER are used by convention to indicate that the value may be arbitrarily large. The values MAX_STRING_LENGTH and MAX_SEQUENCE_LENGTH are used to indicate values limited by the size of a string or the size of a sequence.
      Overrides:
        `getIntegerBounds` in class `Expression`
      Returns:
        the lower and upper bounds of integer values in the result, or null to indicate unknown or not applicable.

    - #### copy

          public Expression copy()

      Copy an expression. This makes a deep copy.
      Specified by:
        `copy` in class `Expression`
      Returns:
        the copy of the original expression

    - #### evaluateItem

          public AtomicValue evaluateItem(XPathContext context)
                                   throws XPathException

      Evaluate the expression
      Overrides:
        `evaluateItem` in class `Expression`
      Parameters:
        `context` - The context in which the expression is to be evaluated
      Returns:
        the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
      Throws:
        `XPathException` - if any dynamic error occurs evaluating the expression

    - #### equals

          public boolean equals(Object other)

      Is this expression the same as another expression?
      Overrides:
        `equals` in class `UnaryExpression`

    - #### hashCode

          public int hashCode()

      get HashCode for comparing two expressions. Note that this hashcode gives the same result for (A op B) and for (B op A), whether or not the operator is commutative.
      Overrides:
        `hashCode` in class `UnaryExpression`

    - #### toString

          public String toString()

      Represent the expression as a string. The resulting string will be a valid XPath 3.0 expression with no dependencies on namespace bindings.
      Overrides:
        `toString` in class `UnaryExpression`
      Returns:
        the expression as a string in XPath 3.0 syntax

    - #### explain

          public void explain(ExpressionPresenter out)

      Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
      Overrides:
        `explain` in class `UnaryExpression`
      Parameters:
        `out` - the expression presenter used to display the structure

    - #### getExpressionCompiler

          public ExpressionCompiler getExpressionCompiler()

      Return the compiler of the Cast expression
      Overrides:
        `getExpressionCompiler` in class `Expression`
      Returns:
        the relevant ExpressionCompiler

Copyright (c) 2004-2013 Saxonica Limited. All rights reserved.